Food allergy appears to have risen rapidly in prevalence over the past few decades, leading to much research into the causes of this apparent 'epidemic'. Yet, because the data showing increased prevalence are largely based on questionnaires, and we know that questionnaires overestimate clinically confirmed food allergy, we truly do not know how real the apparent epidemic is. It is possible that the increased prevalence seen in the questionnaires represents changes in the diagnosis of food allergy, and that biologic markers of this disease remain unchanged. An additional unknown is whether the growing ethnic/racial disparities in food allergy prevalence seen in the self-reported data relate to true biologic differences. In order to determine whether the trends that are found in self reported food allergy correlate with changes in biologic measures of food allergy, we propose to measure food specific IgE in stored samples from the National Health and Nutrition Examination Survey (NHANES) III, collected from 1988-1994, in order to compare it to that already measured in NHANES 2005-6. Aim 1 is to compare the prevalence of sensitization and higher likelihood of clinical food allergy, both as measured by specific IgE to milk, egg, peanut or shrimp, in U.S. children over this approximately 15 year period. Aim 2 is to test the hypothesis that Non-Hispanic Blacks have experienced greater increases in prevalence of sensitization and higher specific IgE over this period. Combined, these aims will answer fundamental questions in the field of food allergy epidemiology.